Various means are known to sequentially fire a high voltage type photoflash lamp array utilizing a circuit board member having the firing circuitry deposited directly thereon. The use of radiation-sensitive switches and fuse elements connected in said circuitry is also known. A photoflash unit of this general type is described in U.S. Pat. No. 3,894,226, issued July 8, 1975, to James M. Hanson, wherein the particular flash lamps employed provide an open circuit condition between the lead-in wires upon flashing and radiation-sensitive switches permit the next lamp to be flashed. In the aforementioned co-pending application Ser. No. 567,576 an alternative lamp sequencing arrangement is disclosed wherein the flash lamp construction employs a shorting primer material including combustion supporting oxides to establish a sufficient conducting path across the lamp in-leads for the shorted lamp to function thereafter as a conducting element in the flash sequencing circuit. The circuit board member operatively associated with said flash lamps further includes low resistance radiation-sensitive switching devices connected in series with each lamp to open the electrical circuit upon flashing the associated lamp and thereby avoid short circuiting of the high voltage energy source when successive lamps are flashed in the firing sequence.